In the genus Nycteris a curious faculty is observed, namely, the power of inflating the sub cutaneous tissue with air. The skin adheres to the body only at certain points, where it is connected by means of a loose cellular mem brane ; it is therefore susceptible of being raised from the surface, on the back as well as on the under parts. These large spaces are filled with air at the will of the animal, by means of large cheek pouches, which are pierced at the bottom, and thus communicate with the subcutaneous spaces just mentioned. When the animal therefore wishes to inflate its skin, it inspires, closes the nostrils, and then contracting the cavity of the chest, the air is forced through the openings in the cheek pouches under the skin, from whence it is prevented from returning by means of a true sphincter, with which those openings are furnished, and by large valves on the neck and back. By this curious me chanism the bat has the power of so com pletely blowing up the spaces under the skin, as to give the idea, as Geoffroy observes, " of a little balloon furnished with wings, a head, and feet." The digestive organs of the Cheiroptera ex hibit as distinct a division into the two prin cipal groups before-mentioned, as any other part of their anatomy. The teeth have been already alluded to, and the characters of these important organs, important as indicating, in the most unerring manner, the nature of the food, are well-marked in the two groups. The flattened crowns of the molares, so similar to those of the Quadrumana which are found to belong to the frugivorous Bats, are strikingly contrasted with the many-pointed tuberculous teeth of the insect-feeders, and exhibit an in teresting affinity to the two important orders of animals to which the Cheiroptera may be con sidered intermediate; the former division re ferring evidently to the Quadrumanous type in the structure of the teeth, and the latter to the type of the insectivora.
The tongue presents a. peculiarity in the genus Phyllostoma, which is worthy of being particularly noted. It consists of a number of wart-like elevations, so arranged as to form a complete circular suctorial disk, when they are brought into contact at their sides, which is done by means of a set of muscular fibres, having a tendon attached to each of the warts. By means of this curious sucker, these bats are enabled to suck the blood of animals and the juice of succulent fiuits. This power has been attributed by mistake to some of the genus Pteropus, merely because their tongue is rough, and it was calculated that by means of such a surface the skin may have been abraded.
The stomach is no less indicative of the nature of the aliment than the teeth ; offering, in the Pte ropes (fig. 287), a very striking affinity to that of many true vegetable feeders in some remote orders, and in Plecotus (fig. 288), as complete an identity with that of the carnivorous type. In the former the cesophagus swells out before it enters the general cavity, and that dilatation, as Home observes, appears, from its structure, to belong to the stomach. To the left of the cesophagus there are two dilatations, the far thest of which has a smooth surface and thin coats ; the other is furnished with-several deep longitudinal rugw, some of which are con tinued from similar ones in the cesophagus.
Four of the rug-T are continued towards the pylorus, giving a direction to the food in that course; about one-third of the stomach to wards the pyloric extremity is turned back upon itself, and the pylorus is consequently placed externally close to the entrance of the cesophagus. At the pylorus is a very small opening into the intestine, which when con tracted seems scarcely pervious to air. Such is the complicated form of the stomach in the frugivorous division ; whilst that of the insect feeders is as simple as possible, being only divided into a cardiac and a pyloric portion with scarcely the slightest contraction. The intestines present a no less marked distinction. In the Pteropus they are no less than seven times the length of the body, whilst Vesper tilio noctula offers the shortest proportional length of the canal, it being only twice as long as the body. The latter is also wholly devoid of a ccecunz.
The organs qf generation.—The male organs of the Bats bear a near relation to those of the Quadrumana and of Man, in some striking respects. The penis is pendulous, and the proportions between the different organs are not very dissimilar ; but the testes do not descend from the abdomen excepting during the breeding season, when they are found on each side of the anus, whilst the large epididymis is seen just behind them, on each side of the origin of the tail. The vesicula seminales are of moderate size, and consist of two round white sacs, which are perfectly simple, form ing each a single cavity with a secreting in ternal surface. They have a prostate gland, which surrounds the whole circumference of the urethra, and appears to be composed of numerous small lobes. They have also Cow per's glands. The penis is very similar to that of the other more highly organized forms, the Quadrumana and Man. It is of moderate size, pendulous, and supported by ligaments, as in the other cases. There is a small bone of the penis. The muscular portion of the urethra is rather long. The glans is in some species enlarged by a small process or button on each side; the urethra opens at the extreme point.
The female organs offer nothing very par ticular. The vulva is round, and exhibits a slight appearance of a clitoris near its edge ; the mouth of the uterus stands out into the vagina. The uterus is two-horned and the horns are very short.
There are but two teats, which are placed on the breast. •The additional ones said to exist in the groin of the Rhinolophi are most probably ordinary cutaneous glands, as Kuhl could discover no trace of mammary glands beneath them. They were first discovered by Montagu in this country, and by Geoffroy in France.
The Bats are among those animals in whom we notice the remarkable phenomenon of Hy bernation, of which it is unnecessary to say any thing here, as a distinct article is devoted to the subject. (See HYBERNATION.)